1. Field of the Invention
The present invention relates generally to medical devices, and more particularly to a steerable catheter having a segmented tip configured for improved steerability, a tip assembly providing improved resistance to steering wire pull-through, and an improved one-piece inlet housing.
2. Description of Related Art
Medical practitioners frequently gain access to internal regions of a patient's body through the use of medical catheters in a variety of medical procedures, in order to reduce or eliminate the need for more invasive procedures. For example, medical catheters may be used to access internal body regions with a fiberoptic scope, light bundles, and/or other surgical instruments or devices, for a variety of diagnosis, treatment and/or material delivery purposes.
Steerable catheters have been developed to provide improved access to internal tissue. These catheters typically include a flexible catheter shaft and steering wires for controlling the flexure of the catheter shaft. A problem common to many previously existing steerable catheters is the retention of the steering wire or wires within the flexible material of the catheter shaft. The steering wire or wires typically comprise a small diameter length of high tensile strength material, whereas the flexible catheter shaft material typically must be relatively soft in order to provide sufficient flexibility. Thus, in many instances, the steering wire will cut through the flexible catheter shaft material, or will otherwise become disattached from the catheter shaft, rendering the catheter inoperable or compromising its utility. This problem is especially troublesome with small diameter catheters having one or more instrument access lumens therethrough, due to the reduced material thickness of the catheter.
Various approaches have been proposed for addressing the problem of steering wire detachment, a number of which are described in applicant's previous U.S. patent application Ser. Nos. 08/777,548 and 09/126,863, the content of which are incorporated herein by reference. Previously developed devices and methods have met with varying degrees of success, but none have proven fully successful for all applications.
An additional problem that has been found problematic in some previously known catheter designs results from the use of standard Touhy-Borst assemblies 10, as shown in FIG. 1, as the catheter inlet. The standard Touhy-Borst assembly 10 typically comprises a two-piece housing, having a first housing component 12 coupled to a second housing component 14 by means of a threaded luer 16 or other coupling. The use of this type of two-piece housing results in increased assembly time and expense, and presents a risk of detachment during use. Additionally, the coupling 16 permits relative rotational movement between the first housing component 12 and the second housing component 14. This is disadvantageous as it is has been found desirable to maintain the flush port 18 in a fixed position relative to the catheter housing. The standard Touhy-Borst assembly 10 is typically affixed to the catheter housing by means of mounting wings 20 provided on the second housing component 14. Even if the wings 20 are rigidly attached to second housing component 14, the rotational movement permitted at coupling 16 allows movement of the first housing component 12 and the flush port 18 thereof. In addition, the standard Touhy-Borst assembly 10 presents several steps or discontinuities 22a, 22b, 22c within its internal passage. These discontinuities present obstructions to instrument passage, and can result in abrasive wear and tear on sensitive instruments. The standard Touhy-Borst assembly 10 is also less than fully satisfactory for use as a catheter inlet housing, as it typically includes only two mounting wings 20. It has been found desirable to provide additional mounting wings angularly spaced about the circumference of the inlet housing for more accurate positioning. It has also been found desirable to increase the thickness and contact area of the mounting wings to provide more secure attachment to the catheter body housing.
Thus, it has been found that a need exists for an improved steerable catheter device, and for an improved catheter shaft, tip assembly, and inlet housing for catheters. It is to these and other needs that the present invention is primarily directed.